Numerical Analysis of Dynamic Resistance and Total Loss in REBCO-Coated Conductors at Low Temperature Under High Perpendicular AC Magnetic Fields

In several applications of high-temperature superconductors, a REBCO-coated conductor (CC) carries a dc current under varying magnetic fields. This generates ac loss, which can be an important factor to consider in the thermal design of the application. In this work, the dynamic resistance (
R
_dyn
) and total loss in a 4-mm wide Superpower REBCO CC are numerically investigated for ac perpendicular magnetic fields (
B
_m
) up to 1 T and temperatures ranging from 30 to 50 K. For
I
_dc
/
I
_c0
> 0.1 (where
I
_dc
is the dc current level and
I
_c0
is the self-field critical current of the conductor), either of the previously developed equations, the nonlinear or the simple linear expression for determining
B
_th
(threshold magnetic field), can be used to predict
R
_dyn
. Finite dynamic loss is observed even below the
B
_th
points due to the emergence of resistance. The resistance arises from the superposition of subcritical shielding and transport currents, which introduces a finite electric field in the CC. The total loss at higher fields decreases as the temperature increases from 30 to 50 K for all current values, except for
I
_dc
/
I
_c0
= 0.9. A lift-off in the total loss is evident for fields around 1 T for all temperatures investigated.